For an optical communication, an optical transmitting module to convert electric signals into optical signals for transmitting as well as an optical receiving module to convert optical signals into electric signals for receiving are essential.
In addition, the art with which a variety of optical elements for generating, detecting, modulating and distributing functions of a light are attached with optical fibers and packaged is essential for commercializing all sorts of communicating elements.
In the process for packaging optical modules, one of the most difficult and costly steps is that of aligning and fixing an optical fiber in the wave guiding path of an optical element which represents a determinant factor for the cost of an optical communication module.
That rests on the difficulty in spatially aligning an optical element and an optical fiber, and holding the both in the aligned position without displacement in view of the very small area for the optical input or output of an optical element in the order of a few square micrometers and also the small area for the optical input or output of an optical fiber in the order of several tens of square micrometers.
The conventional methods for aligning an optical transmitting module and an optical receiving module may be broadly divided into an active aligning method and a passive aligning method.
However, the active aligning method has a difficulty in cost reduction because it needs a long processing time and many parts due to the use of lenses and an expensive laser welder.
On the other hand, the passive aligning methods can be performed without the use of those lenses and laser welders and therefore are coming to the front as new methods for reducing the price of the optical communication modules.
According to a conventional passive aligning method as shown in FIG. 14, after the chip marker 1022 on the bottom surface of a laser diode chip 1010 is caused to match the substrate marker 1014 on the top surface of a substrate 1000, the laser diode chip 1010 is bonded to the metal junction layer 1012 of the silicon substrate 1000 by using a flip chip bonder.
The method using markers as described above is not much more advantageous in the point of the required time for process as compared to the active aligning method and also has a drawback of an increased installation cost for the equipment like a flip chip bonder.
Another conventional passive aligning method is shown in FIG. 15.
In this method, first a support 2040 loaded with a laser diode chip 2010 is fixed bonded on the surface of a substrate 2030 and then mounts 2050 and 2060 are fixed to the substrate 2030. Subsequently, the optical fiber 2020 is caused to be received, with its end close to the laser diode chip 2010, in the groove 2051 formed on the mount 2050 and then the optical fiber 2020 is aligned in its position with regard to the laser diode chip 2010 by adjusting the position of the end of the optical fiber 2020, which end positions on the side of the mount 2050. When the optical fiber 2020 has been precisely aligned in position through those procedures, the optical fiber 2020 is fixed to the mount 2060, for example, through soldering.
For the optical communication module according to FIG. 15 as described above, the positions in which the mounts and the support will be fixed are not exactly determined and therefore a great deal of time is spent to find optimum fixing positions at the time of mounting work. Nevertheless there arise deviations in the fixing positions depending on the individual products because the mounts or the supports are not exactly positioned.
Accordingly, the position alignment operation for the optical fiber with regard to the laser diode chip is not only difficult but the fixing positions of the mounts and supports with unduly high errors can also cause the problem that the optical fiber is not properly lined up with the axis of the laser diode chip.
An improved optical communication module intended to solve the above-described problem is disclosed in the Korean Patent Application No. 1997-044417.
Referring to FIG. 16 concerning the corresponding art, the art is characterized in that the position determining means 3091, 3092 and 3093 to define the positions in which the support 3040 and the mounts 3050 and 3060 are to be fixed are provided.
In particular, the support 3040 on which the laser diode chip 3010 is mounted is inserted into the first position determining groove 3091 on the substrate 3030 and fixed there through bonding or the like. Then, the mount 3050 is inserted into the second position determining groove 3092 and the mount 3060 is inserted into the third position determining groove 3093 on the substrate 3030 and then fixed through bonding.
Subsequently, after the optical fiber 3020 is placed on the mount 2050 with its end close to the laser diode chip 3010 received in the groove 3051, the optical fiber 3020 is brought into a correct position for alignment with the laser diode chip 3010 by adjusting the position of the optical fiber 3020 at its end part on the side of the mount 3050.
When the optical fiber 3020 has been precisely set in its desired position, the optical fiber 3020 is fixed to the mount 3060 through soldering or the like.
Because the support 3040 and the mounts 3050 and 3060 are fixed after they were inserted into their respective position determining grooves 3091, 3092 and 3093 in the assembling operation as described above, even in the case of mass production of optical communication modules, the positions of the support 3040 and the mounts 3050 and 3060 relative to that of the substrate 3030 can always be maintained definite.